The present invention relates generally to methods and apparatus for measuring runout in cylindrical objects, particularly cutting and boring tools such as drills and reamers.
Runout is a common defect in cutting and boring tools, such as drill bits and reamers, that consists of a bend or curvature in the longitudinal axis of the tool. Runout most commonly develops through use of the tool, although it also occurs occasionally as a manufacturing defect in a new tool. The usual consequence of runout is that the cutting tip of the tool, rather than rotating about its longitudinal axis, orbits in a small circular path about the true axis of rotation of the shank of the tool and that of the machine in which the tool is held. The actual diameter of the circle through which the tip of the tool orbits while so held is the measure of the tool runout, and is referred to in the art as the "total indicated runout".
Heretofore, the manual detection and measurement of runout in cutting tools has been a relatively slow and painstaking process, with the measured runout being subject to substantial individual variation from one machinist to another. There has not been available previously an apparatus for providing a rapid and reliable measurement of runout and which is also suitable for efficiently processing large numbers of tools. There has been a need for such an apparatus, for example, in the aircraft industry where large numbers of closetolerance drill bits are used on a daily basis in precision drilling and riveting production operations.
Accordingly, it is the general object and purpose of the present invention to provide a method and apparatus for detecting and measuring runout in a cylindrical object, particularly a cutting tool such as a drill bit or a reamer. It is a further object to provide a method and apparatus for measuring runout that is rapid, accurate, and independent of the particular operator performing the task.